1. Field of the Invention
The present invention relates to a digital broadcast/analog broadcast receiving apparatus for receiving a digital broadcast signal and an analog broadcast signal and outputting a video signal and a sound signal, and particularly to a digital broadcast/analog broadcast receiving apparatus that updates internal time information thereof based on channel time information of the received channel.
2. Description of the Related Art
A conventional digital broadcast/analog broadcast receiving apparatus includes a circuit for receiving a digital broadcast signal and a circuit for receiving an analog broadcast signal, and when a channel selected is of a digital broadcast, the circuit for digital broadcast is used to convert the digital broadcast signal and outputs a video signal and a sound signal of an analog mode. When the channel selected is of an analog broadcast, the circuit for analog broadcast signal is used to output a video signal and a sound signal of the analog mode.
The digital broadcast/analog broadcast receiving apparatus is equipped with an RTC, which is time control means for controlling internal time information of the apparatus. Based on the internal time information, a timer function such as an automatic power ON function for turning on a power source at a preset time or an automatic switch OFF function for turning off a power source at a preset time works.
However, the RTC that is equipped within the apparatus cannot measure time accurately, and there is also an RTC in which an error of several seconds per day is caused. Therefore, the digital broadcast/analog broadcast receiving apparatus acquires time information (channel time information) inserted into a digital broadcast signal or an analog broadcast signal received and updates time information (internal time information) of the RTC.
In terrestrial broadcast of North America, the digital broadcast signal delivers a difference value between GPS time and UTC time and time information in a GPS format by PSIP information (program information and system information for multiplexing a transport stream) compliant with A65 standard. The digital broadcast/analog broadcast receiving apparatus converts the time information in the GPS format into time information in a UTC format and updates the internal time information of the RTC. Also, the analog broadcast signal delivers time information in a UTC format superposed within the twenty-first scan line (LINE 21) of the video signal compliant with EIA-608 regulation. The digital broadcast/analog broadcast receiving apparatus acquires the time information in the UTC format and updates the time information of the RTC.
However, among digital broadcasts and analog broadcasts which the digital broadcast/analog broadcast receiving apparatus can receive, there are channels in which time information is not included at all or channels such as test stream that delivers time information in which totally different time from the actual time.
Since the digital broadcast/analog broadcast receiving apparatus updates time information of the RTC based on channel time information included in the channel received, when a channel selected includes time information that is not accurate, the time information of the RTC is updated by the inaccurate time information. As a result, time at which a viewer wants the apparatus to be powered ON/OFF differs from time at which the apparatus actually acts.
For example, in the case of making a viewing reservation or a recording reservation using EPG (Electronic Program Guide), due to the difference between the time information of the RTC and the actual time, the viewing reservation or the recording reservation may not be made as the viewer desires.
In the conventional digital broadcast/analog broadcast receiving apparatus, even when a viewer selects a channel for acquiring time information, the channel number selected is only displayed, so that the viewer does not see whether or not the selected channel includes accurate time information, and cannot select a time information setting channel easily.
Various digital broadcast/analog broadcast receiving apparatus have been proposed conventionally, and there are techniques disclosed in Japanese unexamined patent publications JP-A-5-328322 and JP-A-11-027598. However, no method for solving the problem described above is disclosed in the publications.